mjr46

depends on what it is, check the easy stuff first like the pcv system then perform a compression test and leakdown test , then you'll know what you have to work with

blownfiveo17

what should compression be at?

mjr46

as a general rule of thumb at least 100 psi is needed for complete combustion to occur, and you should look for any inconsistencies amongst cylinder readings, generally most 5.0's depending on altitude you are at will come in around 140-150 psi

blownfiveo17

so good compression= rings are ok?

mjr46

compression rings yes, but oil control rings bad would let blow by occur

minnow81469

125-150

1BIGMOFO

COuld be depending on the problem. I had the same issue. The first thing i did was a compression test. If you have a bad ring youll find out right away. If all cyl hold decent compression i would call it valve seals IMO. On my car it was valve seals but it didnt smoke ALL the time. Mostly when i let off the gas. BUT like mjr said a seal could have slid up the stem creating the same problem..

1BIGMOFO

Itll cost you roughly $150 for head bolts, head gaskets and the valve seals. I would just buy a set of heads ready to go. GT40 heads are cheap and youll get a HP gain (after you make the determination if thats the problem)..

blownfiveo17

OK so today i was able to do a little. I checked cylinders 5-8. Readings were..
5. 120
6. 130
7. 115
8. 119

Also there was some oil in the spark plugs when i took them out.

91lx50udlose

after i put new rings/bearings in my engine all cyl. were at 150
i would consider what you have ok to run but i would still consider pulling the motor sending off the heads and go through the bottom end
im not saying the guides/and seals wont help cuz it sounds like they will help tremendously but the rings have wear